Sodium Lauryl Sulfate, or SLS, is found in virtually every major brand of toothpaste. It is an effective and inexpensive detergent.
Unfortunately, it has also been linked (in 3 of 4 independent clinical trials) to a significant increase in number of canker
sores when compared to brushing with SLS-free toothpaste. (Note: The only other common toothpaste ingredient found to indicate a
slightly elevated canker sore risk is Cocoamidopropyl Betaine or CAPB. Verve toothpaste is also CAPB-free).

There have been four clinical trials that have looked at the relationship between canker sores and brushing with toothpaste containing Sodium Lauryl Sulfate ("SLS toothpaste"), versus using a toothpaste without Sodium Lauryl Sulfate ("SLS-free toothpaste"). In the briefest terms,
the results of these trials, with regard to canker sore occurrences are:

Trial 4) Inconclusive: while the study subjects faired better, on average, during SLS-free toothpaste periods than during the
SLS-containing toothpaste periods, the effect was not as pronounced as in the other trials, and the statistical analysis of the
results could not decisively rule out the possibility of a "chance" correlation. In the analysis of number of canker sores, the
probability of a chance correlation was 6.6% (and therefore the probability of a real correlation was 93.4%). By convention, the
probability of a chance correlation must be at or below 5% for the result to be considered statistically significant.